Technical Field
The present disclosure generally relates to optical sensors, and more particularly, to laser scanners and configuration tools for laser scanners.
Description of the Related Art
Optical sensors are currently used in a number of applications for the detection of objects. One type of optical sensor is a laser scanner, in which a collimated light beam generated by a laser source periodically moves over an area to be scanned or monitored. The light beam may be moved by a scanning mirror or other deflection unit which rotates or oscillates to direct light beams over the area. Using the angular position of the scanning mirror, the angular position of an object may be determined. Using the time of flight for pulses of light reflected by an object and the speed of light, the distance of an object may also be determined. From the angular and distance measurements, objects may be detected in the area in two-dimensional polar coordinates, for example.
In addition to object measurement applications, laser scanners may also be used in safety applications for monitoring a source of danger, such as a machine. In such safety applications, a laser scanner may be positioned to monitor an area proximate the source of danger which should not be entered by personnel. If a person or object enters the monitored area when the laser scanner is active, the laser scanner may generate an alarm and/or mitigate the source of danger (e.g., cause shutdown of a running machine).
FIG. 1 shows a schematic sectional view of a laser scanner 10 described in U.S. Pat. Pub. No. 2013/0003041. In operation, a light source 12, such as a laser diode, emits a collimated beam 14 in the form of short (e.g., few nanoseconds) pulses toward a bending or folding mirror 16, which reflects the beam toward a scanning mirror 18, which directs the beam toward a scanning area 20. If an object is present in the scanning area 20, the diffuse light 22 that is back-reflected by the object is reflected by the scanning mirror 18, collected by a collecting lens 24 and detected by a light detector 26 (e.g., a photodiode).
A motor 28 may be operatively coupled to the scanning mirror 18 to drive the scanning mirror in continuous rotation about a vertical axis of rotation. The angular position of the scanning mirror 18 may be detected by an angular position detector 30, such as an encoder. The light beam 14 generated by the light source 12 therefore scans the scanning area 20 generated by the rotational movement. In instances where there is an object in the scanning area 20 and a reflected light signal is detected by the light detector 26, the angular position of the object in the scanning area may be derived from the angular position of the scanning mirror 18, as detected by the angular position detector 30.
The time of flight of individual laser light pulses from their transmission until the reception after reflection by the object in the scanning area 20 may be determined, which allows for calculation of the distance of the object from the laser scanner 10 based on the known speed of light. This evaluation may be performed by a controller 32 which is operatively coupled to the light source 12, the light detector 26, the motor 28, and/or the angular position detector 30. The components of the laser scanner 10 may be arranged in a housing 34 which includes a protective window 36 in the area where light enters and leaves the laser scanner.
Safety laser scanners are often used in environments which are polluted with dust, fog, debris, etc., referred to herein generally as clutter. Such clutter may be detected by a safety laser scanner and interpreted as an actual object (e.g., person), thereby triggering a false alarm. To prevent such undesirable behavior, safety laser scanners may be equipped with a clutter filter which filters or removes clutter signals from the output of the laser scanner so that the clutter is ignored, thereby reducing or eliminating false alarms caused by the presence of clutter within a monitoring area of the scanner. The behavior of the safety laser scanner in a polluted environment may depend on the particular type and amount of clutter (e.g., dust type, fog, debris) present in the environment, which makes it difficult to select an appropriate clutter filter for a particular environment without knowing the particular type and/or amount of clutter in the environment.